SEAN Combs‘ split with his long-suffering ex-girlfriend, Kim Porter, could cost him $1.2 million a year.

Combs agreed to pay one of his baby mamas, Misa Hylton-Brim, $30,000 a month in child support for their son, Justin. But Porter, who stuck with the hip-hop impresario/lothario on and off for 10 years, has three children with him: Christian, 10, and 7-month-old twins D’Lila Star and Jesse James.

“With Misa Hylton-Brim receiving approximately $30,000 a month, there is no reason that Ms. Porter shouldn’t be able to get close to $100,000 or more per month in child support,” celebrity divorce lawyer Raoul Felder told Page Six. “That amount accounts for Porter having three children with Combs and inflation in the years since Misa received the ruling in her case.”

Close friends of Combs also claim that Combs’ wallet is under even more pressure, because he had no pre- or post-nuptial agreement with Porter, who packed her bags two weeks ago and bought a house for herself and her children in Beverly Hills – with Combs’ money, of course.

We didn’t call Combs because he’s lied to us so many times before – most recently denying our story that he and Porter had split, but announcing it several days later – that getting a comment from him will likely result in printing another falsehood.

But the split from Porter hasn’t cramped Combs’ style at all. He was seen out late Wednesday night celebrating DJ Cassidy‘s birthday party at Tenjune.

According to our spies, he arrived at “around 1 a.m. and went straight to the VIP room where he hung out with Kanye West, Jermaine Dupri, Russell Simmons and Andre Harrell.” Combs was also spotted last weekend at Star Room in the Hamptons, where he was “canoodling with a brunette in a cabana with three bodyguards blocking him from fans and paparazzi.”

That kind of behavior frustrated Porter. Just days after she gave birth to their twins, Combs started partying like crazy – going out almost every night with pal Sienna Miller and others into the wee hours.

“He was never home. He said he would slow down a bit, but didn’t at all,” a pal said. Porter is now in Louisiana shooting a movie.